Fuse circuit breaker



June 19, 1956 o. MARKOWITZ FUSE CIRCUIT BREAKER 2 Sheets-Sheet 2 Filed July 7, 19

.IIIIII II III INVENTOR.

OSCAR MARKOWiTZ F W A T TORNEYS FUSE CIRCUIT BREAKER @scar Markowitz, Philadelphia, Pa.

Application July 7, 1954, Serial No. 441,953?

9 Claims. (Cl. Mitt-11? (Granted under "run 35, U. S. (lode (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon: or therefor.

The present invention relates to a fuse circuit breaker and more particularly to a fuse circuit breaker of the trip tree variety operated by temperature responsive bimetallic strips functioning both. as the sensing mechanism and also as the contact operating mechanism.

The circuit breaker assemblies disclosed in the prior art all have one general characteristic in common in that each includes a condition sensing mechanism operable in response to a critical change in condition to trip a relatively complicated contact operating mechanism operable to break the contacts in response to the tripping action of the sensing mechanism. Moreover, in known devices wherein the contacts are operated by bimetallic elements, the contacts have been arranged so that they tend to separate with an increase of temperature, thereby decreasing contact pressure as the temperature increases and, at some critical temperature, contact separation occurs. However, since the approach to this critical. condition is accompanied by a steadily decreasing contact pressure, the actual separation is indistinct and unstable. Because this characteristic instability at the instant of contact separation may have serious consequences, it has resulted in the development of many devices designed to overcome this disadvantage which only tend to further complicate existing circuit breaker assemblies.

In contrast to these deficiencies of known types of circuit breaker assemblies, the present invention contemplates a configuration which relies upon a principle of operation contrary to that noted above, generally used in designing devices in which the contacts are supported by bimetallic elements. In the instant invention the two temperature responsive bimetallic strips arranged to support the respective contacts are so disposed that they tend to press the contacts together with increasing force as the temperature increases until, at the instant of separation, the contacts snap apart and move away from each other rapidly, thereby avoiding instability and indistinct contact action at the critical temperature at which disengagement of the contacts is desired.

An object of the present invention is the provision of a circuit breaker assembly readily interchangeable with the conventional generally cylindrical cartridge type fuse assemblies presently in use in many types of electrical and elcctronical equipment.

Another object is to provide a compact lightweight circuit breaker assembly including a limited number of relatively simple components.

A further object of the invention is the provision of an improved circuit breaker assembly in which instability at the instant of contact separation is eliminated by the provision of means for increasing the contact pressure as the temperature increases until contact separation occurs.

2,75ifi62 Patented June 19, 1%56 Still another object is to provide a circuit breaker assembly which may readily be reset by a simple manual operation.

A final object of the present invention is the provision of a circuit breaker assembly which may readily be provided with a simple means for indicating when the contacts have separated.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification in con nection with the annexed drawings in which:

Fig. 1 is a longitudinal cross section of a preferred embodiment of the present invention,

Fig. 2 is a partially broken away perspective view showinga detailed feature of the preferred embodiment shown in Fig. I,

Fig. 3 is a broken away side elevation showing the contacts in the relative positions they assume immediately before they separate,

Figs. 4, 5, 6, and 7, are cross sectional views taken on line 4- i of Fig. l and show the relative positions of the respective contacts beginning with the position they assume after separation and ending with the position they initially assume after they are engaged by resetting the instant invention,

Fig. 8 is a partially broken away longitudinal sectional view showing an additional feature which may be incorporated in the present invention as a modification of the showing in Fig. 1, and

Fig. 9 is a partially broken away perspective view showing an additional detailed feature which may be incorporated for use in connection with the modification shown in Fig. 8.

Referring now to the drawings, wherein like reference characters designate like or corresponding parts throughout the several views, Fig. 1 shows a preferred embodiment of the present invention housed in a container generally designated by the reference numeral 111 of a size and shape corresponding to the well known cartridge type fuse. Two curved bimetallic strips 12 and 14 are shaped at one end to be rotatably mounted on fixed pivots id and 18, respectively, and are provided at the other end with fixedly secured contacts 20 and 22, respective-ly. In addition, the bimetallic strip 14 is provided with a flat generally C-shaped hook 24 mounted adjacent the contact 22 in the manner shown best in Fig. 3 and Figs. 4 through 7 for the purpose of engaging the end of bimetallic strip 12 and contact 20 during the resetting operation. The free end of the C-shaped hook 24 may be fitted with a projecting pin 26 mounted as shown in Fig. l and in Figs. 2 through 7 for use in a manner to be described below in connection with the operation of the present invention. The pivots 16 and 18 are mounted upon the frames 23 and 50 respectively, in turn fixedly secured to the metal end portions 32 and 34 of the housing ii. The remainder of the housing 11 comprises a cylindrical body 36 composed of insulating material upon which the end portion 32 is rotatably mounted and the end portion 34 is fixedly mounted. The bimetallic strips 12 and 14 are connected to the pivot supporting frames by means of flexible leads 38 and 40, respectively, and biasing springs 42 and 44 fastened to the end portions 32 and 34, respectively, are arranged to apply biasing pressure to the bimetallic strips 12 and 14, respectively, in the manner best indicated in Fig. 1. Since relative rotation of the respective contacts during the resetting operation must be in the direction indicated in Fig. 4 in relation to the position of the C-shaped hook 24 for proper completion of the resetting operation the rotatably mounted end portion 32 is free to rotate in one direction only, due to the provision of the detent 43 in the grantee end portion 32 and the cooperating groove t and notch 2 therein extending about the periphery of the cylindrical body 36 as indicated in Figs. 1 and 2. To insure optimum performance of the present invention all of the surfaces about the respective contacts and the adjacent ends of the respective bimetallic strips may be covered by a suitable heat resistant non-conducting material such as fire resisting enamel or the like designated in Fig. 1 by the reference numeral 54.

In normal operation of the present invention, the contacts 2G and 22 are maintained in engagement with each other in the position shown in Fig. l and in Fig. 7, and a substantial contact pressure is provided by the respec tive biasing springs 42 and 44 acting through the bimetallic strips 12 and 14, respectively. With the various components of the present invention arranged in this mannor, an electric current may pass through the metallic end portion 32 and the metal frame 28 secured thereto to the flexible lead 38 and thence to the bimetallic strip 12 and the contact 23 secured thereto. With the contact 26 in engagement with contact 22, the electric current is transmitted through contact 22 to the bimetallic strip 14 and thence through the flexible lead 40 to the metal frame 30 and the metallic end portion 34 upon which the frame 3% is mounted, thus completing the circuit through this device. However, when the electric current transmitted through the present invention increases, each of the bimetallic strips is heated with the result that each curved portion thereof is heated to a higher temperature. The two materials combined in each bimetallic strip are so arranged that increased temperature causes the strip to deflect to form a shorter are so that the distance between the pivot upon which the strip is mounted and the contact at the opposite end of the strip is decreased. With the respective bimetallic strips mutually opposed as shown in Fig. 1, the deflection of these strips in response to increased temperature causes the respective contacts to slide laterally in opposite directions in response to increased current until at a given current suitable indentations in the opposite edges of the respective contacts slide into mutual engagement with the contacts in the position illustrated in Fig. 3. Thereafter, in the event of any further increase in the electric current transmitted through the instant invention, the force tending to slide the respective contacts beyond the posiion illustrated in Fig. 3 pro-stresses the bimetallic strips due to the interengagement of the respective indentations under substantially increased contact pressure until the deflection of the bimetallic strips due to increased temperature generates suflicient force to pull the indentations in the respective contacts out of engagement and allow the respective contacts to assume the positions shown in dotted lines in Fig. 1. It will be noted that the contacts will be separated very rapidly due to the Y substantial forces generated immediately prior to their separation. Moreover, any are generated as the result of this interruption of a relatively high electric current is very quickly extinguished, because all of the surfaces adjacent to the respective contacts faces are coated with a non-conductive material such as a fire resistant enamel 54 and also because the faces of the respective contacts face away from each other as shown in Fig. 4 as soon as they are separated.

After the contacts have been placed in the respective positions shown in Fig. 4 by the imposition of an overload condition upon this device, it may be removed from its holder and reset by rotating the movably mounted portion 32 through 360 in order to move the contact 2% through the series of positions shown best in Figs. 5 through 7 to restore the normal engagement of contact 22 with contact 2t) as shown in Fig. 7. The direction in which the end portion 32 is to be rotated is, of course,

determined by the detent 48 in engagement with the recess 52 in the groove 50. The first 180 of rotation of the end portion 32 brings the contact 29 into engagement with the C-shaped hook 24 as shown in Fig. 5, and as rotation is continued past 180 the rotating contact 2 in engagement with the book 24 forces the bimetallic strips supporting the respective contacts to adjust themselves toward their normal mutually opposed position through the relative positions shown in Fig. 6 and ending upon the completion of 360 rotation with both contacts in engagement and with the ends of the respective bimetallic strips supporting the contacts positioned centrally of the cylindrical body 36 as shown in Fig. 7. If the excessive current which originally opened the contacts exists when the present invention is reset and replaced, it will be opened again since the contacts cannot be held in the closed position in the presence of such an overload condition. Thus, this invention may be designated as a circuit breaker assembly of the trip free variety.

The present invention can also be modified as shown in Fig. 8 to include a shaft projection 62 extending from the rotatable end portion 32 and fitted with a knob 64 secured to the end of the shaft projection by suitable fastening means. However, such a modification of the present invention would require the use of a holder adapted to receive such a shaft projection and provide access to the knob 64. When the contacts have been separated by operation of the present invention in the modified form shown in Fig. 8 the knob 64 can be rotated 360 to reset the contacts without removing the housing 11 from the holder in which it is mounted. Where this modification is used without removing the circuit breaker assemly from the holder, it is desirable to provide a further modification of the rotatable end portion 32 as shown in Fig. 9 so that the circuit in which the circuit breaker assembly is incolporated is broken at the start of the reset rotation of end portion 32 and is not restored until the circuit breaker is in its reset position. The showing in Fig. 9 illustrates one simple arrangement for providing this fea ture in which the end portion 32 is provided with a projecting tab 72 for engagement with a sliding contact 74 connected to the external portion of the circuit in which the circuit breaker assembly is incorporated. With the arrangement shown in Fig. 9, the initiation of the resetting movement moves the tab 72 out of engagement with the sliding contact 74 for almost the entire 360 rotation and restores the tab 72 to engagement with the contact 74 upon completion of the resetting movement.

In order to meet the specific needs of various applications, the exact load at which the contacts 20 and 22 separate may be adjusted readily by inserting one or more calibrating shims 31 of the necessary thickness between the end of the intermediate portion 36 and the fixedly mounted end portion 34 of the housing 11.

The present invention can readily be modified to incorporate an auxiliary feature such as an independent contact plate to operate a signal circuit when the circuit breaker has operated to disengage the contacts. This feature can be provided by mounting a small auxiliary contact plate 30 upon the cylindrical body 36 in a position in which it will be contacted by the face of contact 20 when it is disengaged from contact 22 to complete the necessary auxiliary circuit.

The present invention may also be readily modified to provide for the operation of auxiliary mechanical devices after the circuit breaker has been tripped. This additional feature may be provided by locating a suitable switch mechanism adjacent to the cylindrical housing 36 so that it may be engaged by the pin 26 when it projects through a suitable opening in the wall of the cylindrical body 36. In the form illustrated, the switching means comprises a pair of fixed contacts 92 and 94 and a movable contact 96 controlled by a spring 93 disposed so that it may be engaged by the pin 26.

When the modification shown in Fig. 8 is used, the circuit breaker assembly comprising the present invention can also be used as a switch by arranging the knob 64 and the attached end portion 32 so that it can be moved manually away from the cylindrical body 36 a short distance by overcoming a biasing spring tending to hold it in engagement with the cylindrical body 36. With such a configuration, the on position is obtained by 360 rotation of the end portion 32 by means of the knob 64 and the off position is obtained manually by pulling the knob 64 away from the cylindrical portion 36 to disengage the respective contacts.

Thus, the present invention provides a relatively simple and compact circuit breaker assembly which is readily interchangeable with the conventional cartridge type fuse and has its component parts inherently balanced so that it is especially suitable for use under severe environmental conditions such as shock and vibration, yet it may be reset readily by a simple manual operation.

Obviously additional modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A circuit breaker for use as a replacement for a conventional cylindrical fuse, including a pair of axially aligned elongated electrically conductive members normally in contact with each other and arranged to be inserted in an electrical circuit, at least one of which is an arcuately curved bimetallic member pivotally mounted at one end and normally in contact with the other member at its other end, biasing means adjacent said bimetallic member for continuously deflecting said bimetallic member toward the other member, said bimetallic member being arranged to deflect arcuately in response to heat generated by excessive electric current to an increasingly curved configuration so that it bears against the other member with increased pressure until it becomes sufficiently foreshortened to slide ofi and move rapidly away from the other member, and means operable, as one member is rotated through 360 relative to the other, to restore the normal contact between said members.

2. A circuit breaker for use as a replacement for a conventional cylindrical fuse, including a pair of elongated bimetallic members, a pair of mounting means located at opposite ends of a cylindrical fuse-type container, to each of which one end of the respective bimetallic members is pivotally connected, a pair of spring biasing means arranged to bias the free ends of the respective bimetallic members toward each other, contact portions on the free ends of the respective bimetallic members normally pressed against each other at a point substantially in alignment with said mounting means, each said bimetallic member being arcuately curved from its pivotal connection to said mounting means toward the contact portion at its free end and arranged to deflect arcuately so that it is increasingly curved and foreshortened in response to heat generated by excessive electric current whereby its contact presses with increased pressure against that of the other member and moves toward the pivotally mounted end of said memher until the respective contacts are moved slidably out of engagement, and guide means mounted upon one of said members operable, as one member is rotated through 360 relative to the other, to restore the normal contact between said members.

3. A device as described in claim 2, in which said guide means comprises a generally C-shaped member attached at one end to the free end of one of the elongated bimetallic members and disposed so that it lies in a plane substantially perpendicular to the adjacent portion of the bimetallic member to which it is attached, whereby relative rotation of the respective bimetallic members brings the C-shaped member into engagement with the free end of the other bimetallic member.

4; A device as described in claim 2, in which the opposing faces of the respective contacts are provided with grooves extending transversely relative to the respective elongated bimetallic members, whereby relative sliding motion of said contacts is restrained adjacent the point of complete separation of the contacts by interengagement of the respective grooves until sufficient sliding force is developed to overcome the restraint imposed by interengagement of the grooves under the substantial bearing pressure applied, so that the contacts snap apart at a more rapid rate.

5. A device as described in claim 2, and, in addition, a fixed contact mounted upon the container and disposed so that it is engaged by one of the contact portions when the respective contact portions open, whereby the fixed contact may be incorporated in an auxiliary warning circuit to be energized when the contact portions of the circuit breaker separate.

6. A device as described in claim 3, and, in addition, a projecting pin mounted upon the free end of the C- shaped member and arranged to project through a suitable opening in the container when the contact portions separate, whereby said pin may be used to actuate a switch controlling a separate circuit to be energized when the contact portions of the circuit breaker separate.

7. A circuit breaker assembly for use interchangeably with conventional cylindrical fuses, comprising a container which includes an elongated hollow cylindrical intermediate portion composed of electrically insulating material and two electrically conductive end portions one mounted fixedly upon one end of the intermediate portion and the other mounted rotatably on the other end thereof, a pair of electrically conductive mounting means each attached to one of the end portions, a pair of elongated arcuately curved bimetallic members each rotatably supported at one end upon one of said mounting means, a pair of spring biasing means each engaging one of said bimetallic members and arranged to bias the free ends of the respective bimetallic members toward each other, a pair of electrical contacts each mounted securely upon the free end of one of the bimetallic members and arranged so that they are normally pressed into mutual engagement by the spring biasing means, each said bimetallic member being arranged to deflect arcuately in response to heat generated by electric current passed therethrough in such a way that the contact secured thereto is pressed with increased pressure against the contact mounted upon the other bimetallic member and moves toward the rotatably mounted end of the bimetallic member upon which it is mounted until the flow of electric current becomes excessive when the respective contacts are moved slidably out of mutual engagement, and guide means mounted adjacent the contact on one of the bimetallic members and operable, when one of the end portions and the bimetallic member attached thereto is rotated through one revolution relative to the other, to restore the normal engagement between the respective contacts.

8. A device as described in claim 7, and, in addition, a projecting member mounted centrally of the rotatably mounted end portion to project outwardly from the end portion, and a control knob fixedly secured to the outer end of said projecting member by suitable attachment means, whereby the rotatably mounted end portion may be manually rotated one revolution to reengage the contacts without removing the circuit breaker assembly from its holder.

9. A device as described in claim 8, and, in addition. an electrically conductive tab attached to the rotatably mounted end portion and arranged to extend a short distance along the outer surface of the intermediate portion toward the other end portion, whereby the holder in which the circuit breaker assembly is mounted may be arranged so that an electrical connection with the 7 8 rotatably mounted end portion is established through References Cited in the file of this patent said tab whenthe contacts are disposed in their normal UNITED STATES PATENTS mutually engaged posrtlons and lnterrupted durlng the revolution of the rotatably mounted end portion to reen- 1303203 Nelson 1931 gage the contacts after they are separated by an excessive 5 2,458,804 Sundt 1949 flow of electric current Blonder p 

